1. Field of the Invention
The present invention relates generally to the field of infusion pumps. More specifically, the present invention discloses an infusion pump capable of administering a series of dosages of liquid medication.
2. Statement of the Problem
Infusion pumps have been widely used for many years to administer antibiotics and other medications to patients. Syringe-type infusion pumps generally include a piston or plunger that slides within a housing to dispense medication. A valve or flow restrictor regulates the flow rate from the pump. Some conventional infusion pumps are driven by a spring, while other infusion pumps require manually pressure to dispense medication.
Another type of conventional infusion pump is vacuum-powered. The pump consists of fluid chamber and a vacuum chamber. Both chambers are equipped with sliding pistons that are mechanically connected (e.g., by a rod) so that a partial vacuum is created in the vacuum chamber as medication is introduced into the fluid chamber. The fluid chamber can be filled either by injecting medication under pressure, or by exerting a force on the fluid chamber piston to simultaneously draw medication into the fluid chamber and create a partial vacuum in the vacuum chamber. After the medication has been loaded into the fluid chamber, the reduced pressure in the vacuum chamber exerts pressure via the pistons and connecting rod that tends to expel medication from the fluid chamber.
Conventional infusion pumps are designed to dispense a single dose of medication, and then must be reloaded for any subsequent doses. This requires additional effort by the healthcare provider. It may entail extra expense if a new infusion pump is used for each dose, or may increase the risk of contamination if the same infusion pump is reused.
Multi-dose infusion pumps have been used in the past in the healthcare industry. However, the multi-dose infusion pumps in common use have substantial shortcomings in terms of complexity, cost, reliability, and ease of use. For example motor-driven infusion pumps can provide flexibility in terms of regulating a series of dosages to be administered to the patient. However, motor-driven infusion pumps tend to be relatively expensive and are complex to use and maintain. Therefore, a need exists in the healthcare industry for an inexpensive, disposable multi-dose infusion pump that is also easy to use.
3. Prior Art
Multi-dose infusion pumps, syringes, and related fluid-dispensing devices that have been used in the past include the following:
______________________________________ Inventor Patent No. Issue Date ______________________________________ Drypen et al. 5,318,544 June 7,1994 Ishikawa 5,178,609 Jan. 12, 1993 Zdeb 5,135,500 Aug. 4, 1992 Wender et al. 5,024,661 June 18, 1991 LeFevre 4,997,420 Mar. 5, 1991 Chang 4,991,742 Feb. 12, 1991 Gangemi 4,966,585 Oct. 30, 1990 Borchard 4,962,868 Oct. 16, 1990 Raphael et al. 4,832,694 May 23, 1989 Vaillancourt 4,813,937 Mar. 21, 1989 France 2,561,925 Oct. 4, 1985 Oshikubo 4,467,942 Aug. 28, 1984 Sanchez 4,050,459 Sep. 27, 1977 Bull et al. 3,492,876 Feb. 3, 1970 France 1,156,298 May 14,1958 Kapelsohn 2,792,834 May 21, 1957 Mathis 2,428,577 Oct. 7, 1947 ______________________________________
Drypen et al. disclose a metering syringe with a plunger having a series of stop surfaces spaced along its length that contact a stop on the syringe tube. The stop surfaces halt forward movement of the plunger at predetermined intervals. The stop surfaces are angularly displaced about the longitudinal axis of the plunger, so that incremental rotation of the plunger permits the plunger to be advanced to the next stop surface.
Ishikawa discloses a medical liquid injector for continuous transfusion that includes a syringe fitted with a piston having a detachable shaft rod, and a cap that can be connected to the proximal end of the syringe. The cap has an elastic pressing device (i.e., a spring) for continuously pressing the piston (after the shaft rod has been remove).
Zdeb discloses an example of a vacuum-powered infusion pump.
Wender et al. disclose a hypodermic syringe having a plunger shaft with a series of horizontal locking grooves. These grooves halt forward movement of the plunger within the syringe barrel at predetermined intervals. At each stop, the plunger must be rotated by 180 degrees to proceed to the next stop.
LeFevre, Gangemi, and Chang disclose examples of spring-powered infusion pumps.
Borchard discloses an apparatus for dispensing a controlled dose of liquid medication that includes a dispenser head which fits over the needle-end of a syringe, and a tube slidably engaged to the dispenser head which encases the piston-end of the syringe. Sliding the tube forward pushes the syringe piston and thereby dispenses liquid from the syringe. The amount of liquid dispensed can be controlled by the pin and slot arrangement between the dispenser head and tube shown in FIGS. 3a and 3b of the Borchard patent.
Raphael et al. disclose a programmed action hypodermic syringe having at least one pin protruding into the bore of the barrel that slidably engages a tracking groove in the plunger.
Vaillancourt discloses an infusion pump powered by an elastomeric bladder.
French Patent No. 2,561,925 discloses a syringe for dispensing a series of doses of medication. As shown in FIGS. 2-5 of this patent, a pin and slot arrangement between the syringe barrel and piston limits the forward motion of the syringe piston and thereby determines the size of each dose. The embodiment shown in FIG. 3 of this patent uses a slot with a series of steps. This embodiment would require that the piston be rotated slightly before dispensing the next dose.
Oshikubo discloses a repeating liquid dispenser having a tubular main body, an actuating member slidably disposed in the main body, and a pressure button on the end of the actuating member projecting out of the upper end of the main body. A spring-loaded rack and pawl mechanism is used to incrementally dispense a quantity of liquid each time that the actuating member is depressed.
Sanchez discloses a hypodermic syringe for administering a plurality of measured doses that includes a barrel and plunger. The size of each dose is controlled by a pin and track mechanism between the barrel and plunger. The track has a plurality of steps controlling forward motion of the plunger within the barrel.
Bull et al. disclose an aliquant discharge device having a syringe with a plunger and a side arm in the upper section of the syringe barrel. In use, the plunger is withdrawn beyond the side arm and suction draws up a blood sample into the syringe. The plunger is then depressed cutting off the vacuum and trapping a known amount of blood in the syringe barrel. This blood specimen is then aliquoted by means of metal stops affixed to the upper end of the plunger that abut on a series of steps as shown in FIGS. 3A-3E of Bull et al.
French Patent No. 1,156,298 discloses another example of a hypodermic syringe with a track mechanism having a series of steps for controlling forward motion of the syringe piston.
Kapelsohn discloses another example of a syringe with a pin and track mechanism to fix the amount of liquid dispensed.
Mathis discloses a liquid-measuring dispenser with a pin and track mechanism for controlling the amount of liquid dispensed.
4. Solution to the Problem
None of the prior art references discussed above show a multi-dose infusion pump having a progression of raised steps on a piston and a rotating cap with a number of stops to selectively engage one set of these steps to dispense a predetermined dose, as shown in the present invention. In particular, none of the prior art shows a multi-dose infusion pump that further includes an arrangement of guides for the cap stops to help ensure that the dosages are administered in proper sequence.